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Sionov RV, Ahdut-HaCohen R. A Supportive Role of Mesenchymal Stem Cells on Insulin-Producing Langerhans Islets with a Specific Emphasis on The Secretome. Biomedicines 2023; 11:2558. [PMID: 37761001 PMCID: PMC10527322 DOI: 10.3390/biomedicines11092558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 09/06/2023] [Accepted: 09/14/2023] [Indexed: 09/29/2023] Open
Abstract
Type 1 Diabetes (T1D) is a chronic autoimmune disease characterized by a gradual destruction of insulin-producing β-cells in the endocrine pancreas due to innate and specific immune responses, leading to impaired glucose homeostasis. T1D patients usually require regular insulin injections after meals to maintain normal serum glucose levels. In severe cases, pancreas or Langerhans islet transplantation can assist in reaching a sufficient β-mass to normalize glucose homeostasis. The latter procedure is limited because of low donor availability, high islet loss, and immune rejection. There is still a need to develop new technologies to improve islet survival and implantation and to keep the islets functional. Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells with high plasticity that can support human pancreatic islet function both in vitro and in vivo and islet co-transplantation with MSCs is more effective than islet transplantation alone in attenuating diabetes progression. The beneficial effect of MSCs on islet function is due to a combined effect on angiogenesis, suppression of immune responses, and secretion of growth factors essential for islet survival and function. In this review, various aspects of MSCs related to islet function and diabetes are described.
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Affiliation(s)
- Ronit Vogt Sionov
- The Institute of Biomedical and Oral Research (IBOR), Faculty of Dental Medicine, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Ronit Ahdut-HaCohen
- Department of Medical Neurobiology, Institute of Medical Research, Hadassah Medical School, The Hebrew University of Jerusalem, Jerusalem 9112102, Israel;
- Department of Science, The David Yellin Academic College of Education, Jerusalem 9103501, Israel
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2
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Archer E, Pavela G, McDonald S, Lavie CJ, Hill JO. Cell-Specific "Competition for Calories" Drives Asymmetric Nutrient-Energy Partitioning, Obesity, and Metabolic Diseases in Human and Non-human Animals. Front Physiol 2018; 9:1053. [PMID: 30147656 PMCID: PMC6097573 DOI: 10.3389/fphys.2018.01053] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 07/16/2018] [Indexed: 12/20/2022] Open
Abstract
The mammalian body is a complex physiologic “ecosystem” in which cells compete for calories (i.e., nutrient-energy). Axiomatically, cell-types with competitive advantages acquire a greater number of consumed calories, and when possible, increase in size and/or number. Thus, it is logical and parsimonious to posit that obesity is the competitive advantages of fat-cells (adipocytes) driving a disproportionate acquisition and storage of nutrient-energy. Accordingly, we introduce two conceptual frameworks. Asymmetric Nutrient-Energy Partitioning describes the context-dependent, cell-specific competition for calories that determines the partitioning of nutrient-energy to oxidation, anabolism, and/or storage; and Effective Caloric Intake which describes the number of calories available to constrain energy-intake via the inhibition of the sensorimotor appetitive cells in the liver and brain that govern ingestive behaviors. Inherent in these frameworks is the independence and dissociation of the energetic demands of metabolism and the neuro-muscular pathways that initiate ingestive behaviors and energy intake. As we demonstrate, if the sensorimotor cells suffer relative caloric deprivation via asymmetric competition from other cell-types (e.g., skeletal muscle- or fat-cells), energy-intake is increased to compensate for both real and merely apparent deficits in energy-homeostasis (i.e., true and false signals, respectively). Thus, we posit that the chronic positive energy balance (i.e., over-nutrition) that leads to obesity and metabolic diseases is engendered by apparent deficits (i.e., false signals) driven by the asymmetric inter-cellular competition for calories and concomitant differential partitioning of nutrient-energy to storage. These frameworks, in concert with our previous theoretic work, the Maternal Resources Hypothesis, provide a parsimonious and rigorous explanation for the rapid rise in the global prevalence of increased body and fat mass, and associated metabolic dysfunctions in humans and other mammals inclusive of companion, domesticated, laboratory, and feral animals.
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Affiliation(s)
| | - Gregory Pavela
- The University of Alabama at Birmingham, Birmingham, AL, United States
| | | | - Carl J Lavie
- School of Medicine, John Ochsner Heart and Vascular Institute, The University of Queensland, New Orleans, LA, United States
| | - James O Hill
- Center for Human Nutrition, University of Colorado Health Sciences Center, Denver, CO, United States
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3
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Bensellam M, Jonas JC, Laybutt DR. Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions. J Endocrinol 2018; 236:R109-R143. [PMID: 29203573 DOI: 10.1530/joe-17-0516] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 12/04/2017] [Indexed: 12/13/2022]
Abstract
Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.
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Affiliation(s)
- Mohammed Bensellam
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Jean-Christophe Jonas
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - D Ross Laybutt
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- St Vincent's Clinical SchoolUNSW Sydney, Sydney, New South Wales, Australia
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4
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Chen Y, Carlessi R, Walz N, Cruzat VF, Keane K, John AN, Jiang FX, Carnagarin R, Dass CR, Newsholme P. Pigment epithelium-derived factor (PEDF) regulates metabolism and insulin secretion from a clonal rat pancreatic beta cell line BRIN-BD11 and mouse islets. Mol Cell Endocrinol 2016; 426:50-60. [PMID: 26868448 DOI: 10.1016/j.mce.2016.02.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 01/23/2016] [Accepted: 02/05/2016] [Indexed: 02/05/2023]
Abstract
Pigment epithelium-derived factor (PEDF) is a multifunctional glycoprotein, associated with lipid catabolism and insulin resistance. In the present study, PEDF increased chronic and acute insulin secretion in a clonal rat β-cell line BRIN-BD11, without alteration of glucose consumption. PEDF also stimulated insulin secretion from primary mouse islets. Seahorse flux analysis demonstrated that PEDF did not change mitochondrial respiration and glycolytic function. The cytosolic presence of the putative PEDF receptor - adipose triglyceride lipase (ATGL) - was identified, and ATGL associated stimulation of glycerol release was robustly enhanced by PEDF, while intracellular ATP levels increased. Addition of palmitate or ex vivo stimulation with inflammatory mediators induced β-cell dysfunction, effects not altered by the addition of PEDF. In conclusion, PEDF increased insulin secretion in BRIN-BD11 and islet cells, but had no impact on glucose metabolism. Thus elevated lipolysis and enhanced fatty acid availability may impact insulin secretion following PEDF receptor (ATGL) stimulation.
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Affiliation(s)
- Younan Chen
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia; Key Laboratory of Transplant Engineering and Immunology, NHFPC; Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu, PR China.
| | - Rodrigo Carlessi
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Nikita Walz
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Vinicius Fernandes Cruzat
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Kevin Keane
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Abraham N John
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia 6009, Australia
| | - Fang-Xu Jiang
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia 6009, Australia
| | - Revathy Carnagarin
- School of Pharmacy, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Crispin R Dass
- School of Pharmacy, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia
| | - Philip Newsholme
- School of Biomedical Sciences, CHIRI Biosciences, Curtin University, GPO Box U1987, Perth, Western Australia, Australia.
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5
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Archer E. The childhood obesity epidemic as a result of nongenetic evolution: the maternal resources hypothesis. Mayo Clin Proc 2015; 90:77-92. [PMID: 25440888 PMCID: PMC4289440 DOI: 10.1016/j.mayocp.2014.08.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 08/08/2014] [Accepted: 08/20/2014] [Indexed: 11/15/2022]
Abstract
Over the past century, socioenvironmental evolution (eg, reduced pathogenic load, decreased physical activity, and improved nutrition) led to cumulative increments in maternal energy resources (ie, body mass and adiposity) and decrements in energy expenditure and metabolic control. These decrements reduced the competition between maternal and fetal energy demands and increased the availability of energy substrates to the intrauterine milieu. This perturbation of mother-conceptus energy partitioning stimulated fetal pancreatic β-cell and adipocyte hyperplasia, thereby inducing an enduring competitive dominance of adipocytes over other tissues in the acquisition and sequestering of nutrient energy via intensified insulin secretion and hyperplastic adiposity. At menarche, the competitive dominance of adipocytes was further amplified via hormone-induced adipocyte hyperplasia and weight-induced decrements in physical activity. These metabolic and behavioral effects were propagated progressively when obese, inactive, metabolically compromised women produced progressively larger, more inactive, metabolically compromised children. Consequently, the evolution of human energy metabolism was markedly altered. This phenotypic evolution was exacerbated by increments in the use of cesarean sections, which allowed both the larger fetuses and the metabolically compromised mothers who produced them to survive and reproduce. Thus, natural selection was iatrogenically rendered artificial selection, and the frequency of obese, inactive, metabolically compromised phenotypes increased in the global population. By the late 20th century, a metabolic tipping point was reached at which the postprandial insulin response was so intense, the relative number of adipocytes so large, and inactivity so pervasive that the competitive dominance of adipocytes in the sequestering of nutrient energy was inevitable and obesity was unavoidable.
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Affiliation(s)
- Edward Archer
- Office of Energetics, Nutrition Obesity Research Center, University of Alabama at Birmingham, Birmingham.
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6
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Forlenza GP, Chinnakotla S, Schwarzenberg SJ, Cook M, Radosevich DM, Manchester C, Gupta S, Nathan B, Bellin MD. Near-euglycemia can be achieved safely in pediatric total pancreatectomy islet autotransplant recipients using an adapted intravenous insulin infusion protocol. Diabetes Technol Ther 2014; 16:706-13. [PMID: 25068208 PMCID: PMC4201245 DOI: 10.1089/dia.2014.0061] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Children with severe chronic pancreatitis may undergo total pancreatectomy with islet autotransplantation (TPIAT) to relieve pain while minimizing the risk of postsurgical diabetes. Because overstimulation of transplanted islets by hyperglycemia can result in β-cell loss, we developed a specialized intravenous insulin infusion protocol (IIP) for pediatric TPIAT recipients to maintain euglycemia or near-euglycemia posttransplant. SUBJECTS AND METHODS Our objective was to review glucose control using an IIP specific for TPIAT recipients at a single institution. We reviewed postoperative blood glucose (BG) levels for 32 children 4-18 years old with chronic pancreatitis who underwent TPIAT between July 2011 and June 2013. We analyzed the proportion of BG values in the range of 70-140 mg/dL, mean glucose, glucose variability, and occurrence of hypoglycemia during the IIP; we also evaluated the transition to subcutaneous therapy (first 72 h with multiple daily injections [MDI]). RESULTS During IIP, the mean patient BG level was 116±27 mg/dL, with 83.1% of all values in the range of 70-140 mg/dL. Hypoglycemia was rare, with only 2.5% of values <70 mg/dL. The more recent era (n=16) had a lower mean BG and less variability than the early era (first 16 patients) (P≤0.004). Mean glucose level (116 vs. 128 mg/dL) and glucose variability were significantly lower during the IIP compared with MDI therapy (P<0.0001). CONCLUSIONS Tight glycemic control without excessive severe hypoglycemia was achieved in children undergoing TPIAT using an IIP specifically designed for this population; the ability to maintain BG in target range improved with experience with the protocol.
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Affiliation(s)
- Gregory P. Forlenza
- Department of Pediatrics, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | - Srinath Chinnakotla
- Department of Surgery, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | - Sarah J. Schwarzenberg
- Department of Pediatrics, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | - Marie Cook
- Department of Surgery, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | - David M. Radosevich
- Department of Surgery, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | | | - Sameer Gupta
- Department of Pediatrics, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | - Brandon Nathan
- Department of Pediatrics, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
| | - Melena D. Bellin
- Department of Pediatrics, University of Minnesota Medical Center and Amplatz Children's Hospital, Minneapolis, Minnesota
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7
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Martens GA, Motté E, Kramer G, Stangé G, Gaarn LW, Hellemans K, Nielsen JH, Aerts JM, Ling Z, Pipeleers D. Functional characteristics of neonatal rat β cells with distinct markers. J Mol Endocrinol 2014; 52:11-28. [PMID: 24049066 DOI: 10.1530/jme-13-0106] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Neonatal β cells are considered developmentally immature and hence less glucose responsive. To study the acquisition of mature glucose responsiveness, we compared glucose-regulated redox state, insulin synthesis, and secretion of β cells purified from neonatal or 10-week-old rats with their transcriptomes and proteomes measured by oligonucleotide and LC-MS/MS profiling. Lower glucose responsiveness of neonatal β cells was explained by two distinct properties: higher activity at low glucose and lower activity at high glucose. Basal hyperactivity was associated with higher NAD(P)H, a higher fraction of neonatal β cells actively incorporating (3)H-tyrosine, and persistently increased insulin secretion below 5 mM glucose. Neonatal β cells lacked the steep glucose-responsive NAD(P)H rise between 5 and 10 mM glucose characteristic for adult β cells and accumulated less NAD(P)H at high glucose. They had twofold lower expression of malate/aspartate-NADH shuttle and most glycolytic enzymes. Genome-wide profiling situated neonatal β cells at a developmental crossroad: they showed advanced endocrine differentiation when specifically analyzed for their mRNA/protein level of classical neuroendocrine markers. On the other hand, discrete neonatal β cell subpopulations still expressed mRNAs/proteins typical for developing/proliferating tissues. One example, delta-like 1 homolog (DLK1) was used to investigate whether neonatal β cells with basal hyperactivity corresponded to a more immature subset with high DLK1, but no association was found. In conclusion, the current study supports the importance of glycolytic NADH-shuttling in stimulus function coupling, presents basal hyperactivity as novel property of neonatal β cells, and provides potential markers to recognize intercellular developmental differences in the endocrine pancreas.
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Affiliation(s)
- G A Martens
- Diabetes Research Center, Brussels Free University (VUB), Laarbeeklaan 103, B1090 Brussel, Belgium Department of Clinical Chemistry and Radioimmunology, Universitair Ziekenhuis Brussel, Laarbeeklaan 101, B1090 Brussels, Belgium Department of Medical Biochemistry, Academisch Medisch Centrum, Amsterdam, The Netherlands Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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8
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Assefa Z, Lavens A, Steyaert C, Stangé G, Martens GA, Ling Z, Hellemans K, Pipeleers D. Glucose regulates rat beta cell number through age-dependent effects on beta cell survival and proliferation. PLoS One 2014; 9:e85174. [PMID: 24416358 PMCID: PMC3887027 DOI: 10.1371/journal.pone.0085174] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 11/24/2013] [Indexed: 11/22/2022] Open
Abstract
Background Glucose effects on beta cell survival and DNA-synthesis suggest a role as regulator of beta cell mass but data on beta cell numbers are lacking. We examined outcome of these influences on the number of beta cells isolated at different growth stages in their population. Methods Beta cells from neonatal, young-adult and old rats were cultured serum-free for 15 days. Their number was counted by automated whole-well imaging distinguishing influences on cell survival and on proliferative activity. Results Elevated glucose (10–20 versus 5 mmol/l) increased the number of living beta cells from 8-week rats to 30%, following a time- and concentration-dependent recruitment of quiescent cells into DNA-synthesis; a glucokinase-activator lowered the threshold but did not raise total numbers of glucose-recruitable cells. No glucose-induced increase occurred in beta cells from 40-week rats. Neonatal beta cells doubled in number at 5 mmol/l involving a larger activated fraction that did not increase at higher concentrations; however, their higher susceptibility to glucose toxicity at 20 mmol/l resulted in 20% lower living cell numbers than at start. None of the age groups exhibited a repetitively proliferating subpopulation. Conclusions Chronically elevated glucose levels increased the number of beta cells from young-adult but not from old rats; they interfered with expansion of neonatal beta cells and reduced their number. These effects are attributed to age-dependent differences in basal and glucose-induced proliferative activity and in cellular susceptibility to glucose toxicity. They also reflect age-dependent variations in the functional heterogeneity of the rat beta cell population.
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Affiliation(s)
- Zerihun Assefa
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Astrid Lavens
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Christophe Steyaert
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Geert Stangé
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Geert A Martens
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Zhidong Ling
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Karine Hellemans
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
| | - Daniel Pipeleers
- Diabetes Pathology and Therapy Unit, Diabetes Research Center and Center for Beta Cell Therapy, Brussels Free University-VUB, Brussels, Belgium
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9
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Hamze Z, Vercherat C, Bernigaud-Lacheretz A, Bazzi W, Bonnavion R, Lu J, Calender A, Pouponnot C, Bertolino P, Roche C, Stein R, Scoazec JY, Zhang CX, Cordier-Bussat M. Altered MENIN expression disrupts the MAFA differentiation pathway in insulinoma. Endocr Relat Cancer 2013; 20:833-48. [PMID: 24157940 PMCID: PMC3841063 DOI: 10.1530/erc-13-0164] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The protein MENIN is the product of the multiple endocrine neoplasia type I (MEN1) gene. Altered MENIN expression is one of the few events that are clearly associated with foregut neuroendocrine tumours (NETs), classical oncogenes or tumour suppressors being not involved. One of the current challenges is to understand how alteration of MENIN expression contributes to the development of these tumours. We hypothesised that MENIN might regulate factors maintaining endocrine-differentiated functions. We chose the insulinoma model, a paradigmatic example of well-differentiated pancreatic NETs, to study whether MENIN interferes with the expression of v-MAF musculoaponeurotic fibrosarcoma oncogene homologue A (MAFA), a master glucose-dependent transcription factor in differentiated β-cells. Immunohistochemical analysis of a series of human insulinomas revealed a correlated decrease in both MENIN and MAFA. Decreased MAFA expression resulting from targeted Men1 ablation was also consistently observed in mouse insulinomas. In vitro analyses using insulinoma cell lines showed that MENIN regulated MAFA protein and mRNA levels, and bound to Mafa promoter sequences. MENIN knockdown concomitantly decreased mRNA expression of both Mafa and β-cell differentiation markers (Ins1/2, Gck, Slc2a2 and Pdx1) and, in parallel, increased the proliferation rate of tumours as measured by bromodeoxyuridine incorporation. Interestingly, MAFA knockdown alone also increased proliferation rate but did not affect the expression of candidate proliferation genes regulated by MENIN. Finally, MENIN variants with missense mutations detected in patients with MEN1 lost the WT MENIN properties to regulate MAFA. Together, our findings unveil a previously unsuspected MENIN/MAFA connection regarding control of the β-cell differentiation/proliferation balance, which could contribute to tumorigenesis.
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MESH Headings
- Adult
- Aged
- Animals
- Apoptosis
- Blotting, Western
- Carcinoma, Neuroendocrine/genetics
- Carcinoma, Neuroendocrine/metabolism
- Carcinoma, Neuroendocrine/pathology
- Cell Differentiation
- Cell Proliferation
- Chromatin Immunoprecipitation
- Female
- Glucose/pharmacology
- Humans
- Immunoenzyme Techniques
- Insulin-Secreting Cells/metabolism
- Insulin-Secreting Cells/pathology
- Insulinoma/genetics
- Insulinoma/metabolism
- Insulinoma/pathology
- Maf Transcription Factors, Large/antagonists & inhibitors
- Maf Transcription Factors, Large/genetics
- Maf Transcription Factors, Large/metabolism
- Male
- Mice
- Mice, Knockout
- Middle Aged
- Pancreatic Neoplasms/genetics
- Pancreatic Neoplasms/metabolism
- Pancreatic Neoplasms/pathology
- Proto-Oncogene Proteins/antagonists & inhibitors
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins/physiology
- RNA, Messenger/genetics
- RNA, Small Interfering/genetics
- Rats
- Real-Time Polymerase Chain Reaction
- Reverse Transcriptase Polymerase Chain Reaction
- Tumor Cells, Cultured
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Affiliation(s)
- Z Hamze
- INSERM U1052/CNRS UMR5286/Université de Lyon, Lyon1 UMR-S1052, Cancer Research Center of Lyon, Lyon F-69008, France Service de Génétique Moléculaire et Clinique, Hospices Civils de Lyon, Hôpital Edouard Herriot, Lyon F-69437, France UMR 3347/CNRS, U1021/INSERM, Institut Curie, Orsay F-91405, France Service Central d'Anatomie et Cytologie Pathologiques, Hospices Civils de Lyon, Hôpital Edouard Herriot, Lyon F-69437, France Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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10
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Insulin downregulates the expression of the Ca2+-activated nonselective cation channel TRPM5 in pancreatic islets from leptin-deficient mouse models. Pflugers Arch 2013; 466:611-21. [PMID: 24221356 PMCID: PMC3928505 DOI: 10.1007/s00424-013-1389-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 10/04/2013] [Accepted: 10/17/2013] [Indexed: 11/07/2022]
Abstract
We recently proposed that the transient receptor potential melastatin 5 (TRPM5) cation channel contributes to glucose-induced electrical activity of the β cell and positively influences glucose-induced insulin release and glucose homeostasis. In this study, we investigated Trpm5 expression and function in pancreatic islets from mouse models of type II diabetes. Gene expression analysis revealed a strong reduction of Trpm5 mRNA levels in pancreatic islets of db/db and ob/ob mice. The glucose-induced Ca2+ oscillation pattern in db/db and ob/ob islets mimicked those of Trpm5−/− islets. Leptin treatment of ob/ob mice not only reversed the diabetic phenotype seen in these mice but also upregulated Trpm5 expression. Leptin treatment had no additional effect on Trpm5 expression levels when plasma insulin levels were comparable to those of the vehicle-injected control group. In murine β cell line, MIN6, insulin downregulated TRPM5 expression in a dose-dependent manner, unlike glucose or leptin. In conclusion, our data show that increased plasma insulin levels downregulate TRPM5 expression in pancreatic islets from leptin-deficient mouse models of type 2 diabetes.
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11
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Moreno-Asso A, Castaño C, Grilli A, Novials A, Servitja JM. Glucose regulation of a cell cycle gene module is selectively lost in mouse pancreatic islets during ageing. Diabetologia 2013; 56:1761-72. [PMID: 23685457 DOI: 10.1007/s00125-013-2930-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/12/2013] [Indexed: 12/16/2022]
Abstract
AIMS/HYPOTHESIS Transcriptional networks in beta cells are modulated by extracellular signals such as glucose, thereby ensuring beta cell adaptation to systemic insulin demands. Ageing is a main risk factor for type 2 diabetes and has been associated with perturbed expression of genes essential for beta cell function. We aimed to uncover glucose-dependent gene modules in mouse pancreatic islets and investigate how this regulation is affected by ageing. METHODS Global gene expression was assessed in pancreatic islets from young and aged wild-type and Cdkn2a (Ink4a/Arf)-deficient mice exposed to different glucose concentrations. Gene modules were identified by gene ontology and gene set enrichment analysis. RESULTS Gene expression profiling revealed that variations in glucose levels have a widespread and highly dynamic impact on the islet transcriptome. Stimulatory glucose levels induced the expression of highly beta cell-selective genes and repressed the expression of ubiquitous genes involved in stress and antiproliferative responses, and in organelle biogenesis. Interestingly, a module comprising cell cycle genes was significantly induced between non-stimulatory and stimulatory glucose concentrations. Unexpectedly, glucose regulation of gene expression was broadly maintained in islets from old mice. However, glucose induction of mitotic genes was selectively lost in aged islets and was not even restored in the absence of the cell cycle inhibitors p16(INK4a) and p19(ARF), which have been implicated in the restricted proliferative capacity of beta cells with advanced age. CONCLUSIONS/INTERPRETATION Glucose-dependent transcriptional networks in islets are globally conserved during ageing, with the exception of the ability of stimulatory glucose levels to induce a cell cycle gene module.
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Affiliation(s)
- A Moreno-Asso
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Centre Esther Koplowitz, Barcelona, Spain
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Flores-López LA, Díaz-Flores M, García-Macedo R, Ávalos-Rodríguez A, Vergara-Onofre M, Cruz M, Contreras-Ramos A, Konigsberg M, Ortega-Camarillo C. High glucose induces mitochondrial p53 phosphorylation by p38 MAPK in pancreatic RINm5F cells. Mol Biol Rep 2013; 40:4947-58. [PMID: 23657598 DOI: 10.1007/s11033-013-2595-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 04/29/2013] [Indexed: 01/09/2023]
Abstract
Pancreatic β-cell death in type 2 diabetes has been related to p53 subcellular localisation and phosphorylation. However, the mechanisms by which p53 is phosphorylated and its activation in response to oxidative stress remain poorly understood. Therefore, the aim of this study was to investigate mitochondrial p53 phosphorylation, its subcellular localisation and its relationship with apoptotic induction in RINm5F cells cultured under high glucose conditions. Our results show that p53 phosphorylation in the mitochondrial fraction was greater at ser392 than at ser15. This increased phosphorylation correlated with an increase in reactive oxygen species, a decrease in the Bcl-2/Bax ratio, a release of cytochrome c and an increase in the rate of apoptosis. We also observed a decline in ERK 1/2 phosphorylation over time, which is an indicator of cell proliferation. To identify the kinase responsible for phosphorylating p53, p38 mitogen-activated protein kinase (MAPK) activation was analysed. We found that high glucose induced an increase in p38 MAPK phosphorylation in the mitochondria after 24-72 h. Moreover, the phosphorylation of p53 (ser392) by p38 MAPK in mitochondria was confirmed by colocalisation studies with confocal microscopy. The addition of a specific p38 MAPK inhibitor (SB203580) to the culture medium during high glucose treatment blocked p53 mobilisation to the mitochondria and phosphorylation; thus, the release of cytochrome c and the apoptosis rate in RINm5F cells decreased. These results suggest that mitochondrial p53 phosphorylation by p38 MAPK plays an important role in RINm5F cell death under high glucose conditions.
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Affiliation(s)
- Luis A Flores-López
- Unidad de Investigación Médica en Bioquímica, HE, Centro Médico Nacional Siglo XXI. IMSS., Av. Cuauhtémoc 330, Col Doctores, Del. Cuauhtémoc, México, DF, Mexico
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13
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High glucose stimulates glutamate uptakes in pancreatic β-cells. Lab Anim Res 2011; 27:327-31. [PMID: 22232641 PMCID: PMC3251763 DOI: 10.5625/lar.2011.27.4.327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2011] [Revised: 12/02/2011] [Accepted: 12/12/2011] [Indexed: 02/07/2023] Open
Abstract
Pancreatic β-cells are major cells responsible for glucose metabolism in the body. Hyperglycemia is known to be a primary factor in the induction of diabetes mellitus. Glutamate is also an excitatory neurotransmitter in diverse organs. Oxidative stress also plays a pivotal role in the development of diabetes mellitus. However, the effect of hyperglycemia in glutamate uptake in the pancreas is not clear. Furthermore, the relationship between high glucose-induced glutamate uptake and oxidative stress has not been investigated. Therefore, this study was conducted to investigate the effect of high glucose on glutamate uptake in pancreatic β-cells. In the present study, 25 mM glucose stimulated the glutamate uptake in HIT-15 cells of hamster pancreatic β-cells. The treatment of 25 mM glucose and 1 mM glutamate also decreased the cell viability in HIT-15 cells. In addition, the treatment of 25 mM glucose induced an increase of lipid peroxide formation. High glucose-induced increase of LPO formation was prevented by the treatment of antioxidants such as N-acetyl-L-cysteine and quercetin. Furthermore, high glucose-induced stimulation of glutamate uptake and decrease of cell viability were also blocked by the treatment of N-acetyl-L-cysteine and quercetin. In conclusion, high glucose stimulated glutamate uptake via oxidative stress in pancreatic β-cells.
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14
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The level of menadione redox-cycling in pancreatic β-cells is proportional to the glucose concentration: role of NADH and consequences for insulin secretion. Toxicol Appl Pharmacol 2011; 258:216-25. [PMID: 22115979 DOI: 10.1016/j.taap.2011.11.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 10/26/2011] [Accepted: 11/07/2011] [Indexed: 12/25/2022]
Abstract
Pancreatic β-cells release insulin in response to elevation of glucose from basal (4-7mM) to stimulatory (8-16mM) levels. Metabolism of glucose by the β-cell results in the production of low levels of reactive oxygen intermediates (ROI), such as hydrogen peroxide (H(2)O(2)), a newly recognized coupling factor linking glucose metabolism to insulin secretion. However, high and toxic levels of H(2)O(2) inhibit insulin secretion. Menadione, which produces H(2)O(2) via redox cycling mechanism in a dose-dependent manner, was investigated for its effect on β-cell metabolism and insulin secretion in INS-1 832/13, a rat β-cell insulinoma cell line, and primary rodent islets. Menadione-dependent redox cycling and resulting H(2)O(2) production under stimulatory glucose exceeded several-fold those reached at basal glucose. This was paralleled by a differential effect of menadione (0.1-10μM) on insulin secretion, which was enhanced at basal, but inhibited at stimulatory glucose. Redox cycling of menadione and H(2)O(2) formation was dependent on glycolytically-derived NADH, as inhibition of glycolysis and application of non-glycogenic insulin secretagogues did not support redox cycling. In addition, activity of plasma membrane electron transport, a system dependent in part on glycolytically-derived NADH, was also inhibited by menadione. Menadione-dependent redox cycling was sensitive to the NQO1 inhibitor dicoumarol and the flavoprotein inhibitor diphenylene iodonium, suggesting a role for NQO1 and other oxidoreductases in this process. These data may explain the apparent dichotomy between the stimulatory and inhibitory effects of H(2)O(2) and menadione on insulin secretion.
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15
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Affiliation(s)
| | - Adam D. Linstedt
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15232;
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16
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Martens GA, Jiang L, Hellemans KH, Stangé G, Heimberg H, Nielsen FC, Sand O, Van Helden J, Van Lommel L, Schuit F, Gorus FK, Pipeleers DG. Clusters of conserved beta cell marker genes for assessment of beta cell phenotype. PLoS One 2011; 6:e24134. [PMID: 21912665 PMCID: PMC3166300 DOI: 10.1371/journal.pone.0024134] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 08/01/2011] [Indexed: 12/02/2022] Open
Abstract
Background and Methodology The aim of this study was to establish a gene expression blueprint of pancreatic beta cells conserved from rodents to humans and to evaluate its applicability to assess shifts in the beta cell differentiated state. Genome-wide mRNA expression profiles of isolated beta cells were compared to those of a large panel of other tissue and cell types, and transcripts with beta cell-abundant and -selective expression were identified. Iteration of this analysis in mouse, rat and human tissues generated a panel of conserved beta cell biomarkers. This panel was then used to compare isolated versus laser capture microdissected beta cells, monitor adaptations of the beta cell phenotype to fasting, and retrieve possible conserved transcriptional regulators. Principal Findings A panel of 332 conserved beta cell biomarker genes was found to discriminate both isolated and laser capture microdissected beta cells from all other examined cell types. Of all conserved beta cell-markers, 15% were strongly beta cell-selective and functionally associated to hormone processing, 15% were shared with neuronal cells and associated to regulated synaptic vesicle transport and 30% with immune plus gut mucosal tissues reflecting active protein synthesis. Fasting specifically down-regulated the latter cluster, but preserved the neuronal and strongly beta cell-selective traits, indicating preserved differentiated state. Analysis of consensus binding site enrichment indicated major roles of CREB/ATF and various nutrient- or redox-regulated transcription factors in maintenance of differentiated beta cell phenotype. Conclusions Conserved beta cell marker genes contain major gene clusters defined by their beta cell selectivity or by their additional abundance in either neural cells or in immune plus gut mucosal cells. This panel can be used as a template to identify changes in the differentiated state of beta cells.
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Affiliation(s)
- Geert A Martens
- Diabetes Research Center, Vrije Universiteit Brussel, Brussels, Belgium.
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17
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Hectors TLM, Vanparys C, van der Ven K, Martens GA, Jorens PG, Van Gaal LF, Covaci A, De Coen W, Blust R. Environmental pollutants and type 2 diabetes: a review of mechanisms that can disrupt beta cell function. Diabetologia 2011; 54:1273-90. [PMID: 21442161 DOI: 10.1007/s00125-011-2109-5] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 01/07/2011] [Indexed: 12/17/2022]
Abstract
The prevalence of diabetes mellitus is currently at epidemic proportions and it is estimated that it will increase even further over the next decades. Although genetic predisposition and lifestyle choices are commonly accepted reasons for the occurrence of type 2 diabetes, it has recently been suggested that environmental pollutants are additional risk factors for diabetes development and this review aims to give an overview of the current evidence for this. More specifically, because of the crucial role of pancreatic beta cells in the development and progression of type 2 diabetes, the present work summarises the known effects of several compounds on beta cell function with reference to mechanistic studies that have elucidated how these compounds interfere with the insulin secreting capacity of beta cells. Oestrogenic compounds, organophosphorus compounds, persistent organic pollutants and heavy metals are discussed, and a critical reflection on the relevance of the concentrations used in mechanistic studies relative to the levels found in the human population is given. It is clear that some environmental pollutants affect pancreatic beta cell function, as both epidemiological and experimental research is accumulating. This supports the need to develop a solid and structured platform to fully explore the diabetes-inducing potential of pollutants.
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Affiliation(s)
- T L M Hectors
- Department of Biology, Laboratory of Ecophysiology, Biochemistry and Toxicology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
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18
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Porat S, Weinberg-Corem N, Tornovsky-Babaey S, Schyr-Ben-Haroush R, Hija A, Stolovich-Rain M, Dadon D, Granot Z, Ben-Hur V, White P, Girard CA, Karni R, Kaestner KH, Ashcroft FM, Magnuson MA, Saada A, Grimsby J, Glaser B, Dor Y. Control of pancreatic β cell regeneration by glucose metabolism. Cell Metab 2011; 13:440-449. [PMID: 21459328 DOI: 10.1016/j.cmet.2011.02.012] [Citation(s) in RCA: 237] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 01/12/2011] [Accepted: 02/23/2011] [Indexed: 01/09/2023]
Abstract
Recent studies revealed a surprising regenerative capacity of insulin-producing β cells in mice, suggesting that regenerative therapy for human diabetes could in principle be achieved. Physiologic β cell regeneration under stressed conditions relies on accelerated proliferation of surviving β cells, but the factors that trigger and control this response remain unclear. Using islet transplantation experiments, we show that β cell mass is controlled systemically rather than by local factors such as tissue damage. Chronic changes in β cell glucose metabolism, rather than blood glucose levels per se, are the main positive regulator of basal and compensatory β cell proliferation in vivo. Intracellularly, genetic and pharmacologic manipulations reveal that glucose induces β cell replication via metabolism by glucokinase, the first step of glycolysis, followed by closure of K(ATP) channels and membrane depolarization. Our data provide a molecular mechanism for homeostatic control of β cell mass by metabolic demand.
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Affiliation(s)
- Shay Porat
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel; Department of Obstetrics and Gynecology, Hadassah-Hebrew University Medical Center, Mount Scopus, Jerusalem 91240, Israel
| | - Noa Weinberg-Corem
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Sharona Tornovsky-Babaey
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Rachel Schyr-Ben-Haroush
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel; Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Ayat Hija
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Miri Stolovich-Rain
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Daniela Dadon
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Zvi Granot
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Vered Ben-Hur
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Peter White
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Christophe A Girard
- Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford OX1 3QX, UK
| | - Rotem Karni
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Klaus H Kaestner
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Frances M Ashcroft
- Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford OX1 3QX, UK
| | - Mark A Magnuson
- Center for Stem Cell Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0494, USA; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0494, USA
| | - Ann Saada
- Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel
| | - Joseph Grimsby
- Department of Metabolic Diseases, Hoffmann-La Roche, Nutley, NJ 07110, USA
| | - Benjamin Glaser
- Endocrinology and Metabolism Service, Department of Internal Medicine, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel.
| | - Yuval Dor
- Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
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Calcineurin increases glucose activation of ERK1/2 by reversing negative feedback. Proc Natl Acad Sci U S A 2010; 107:22314-9. [PMID: 21135229 DOI: 10.1073/pnas.1016630108] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In pancreatic β cells, ERK1 and ERK2 participate in nutrient sensing, and their activities rise and fall as a function of glucose concentration over the physiologic range. Glucose metabolism triggers calcium influx and release of calcium from intracellular stores to activate ERK1/2. Calcium influx also activates the calcium-dependent phosphatase calcineurin, which is required for maximal ERK1/2 activation by glucose. Calcineurin controls insulin gene expression by ERK1/2-dependent and -independent mechanisms. Here, we show that, in β cells, glucose activates the ERK1/2 cascade primarily through B-Raf. Glucose activation of B-Raf, like that of ERK1/2, is calcineurin-sensitive. Calcineurin binds to B-Raf in both unstimulated and stimulated cells. We show that B-Raf is a calcineurin substrate; among calcineurin target residues on B-Raf is T401, a site of negative feedback phosphorylation by ERK1/2. Blocking calcineurin activity in β cells prevents dephosphorylation of B-Raf T401 and decreases B-Raf and ERK1/2 activities. We conclude that the major calcineurin-dependent event in glucose sensing by ERK1/2 is the activation of B-Raf.
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20
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Wong VSC, Yeung A, Schultz W, Brubaker PL. R-spondin-1 is a novel beta-cell growth factor and insulin secretagogue. J Biol Chem 2010; 285:21292-302. [PMID: 20442404 PMCID: PMC2898385 DOI: 10.1074/jbc.m110.129874] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Indexed: 12/13/2022] Open
Abstract
R-spondin-1 (Rspo1) is an intestinal growth factor known to exert its effects through activation of the canonical Wnt (cWnt) signaling pathway and subsequent expression of cWnt target genes. We have detected Rspo1 mRNA in murine islets and the murine MIN6 and betaTC beta-cell lines, and Rspo1 protein in MIN6 beta-cells. Rspo1 activated cWnt signaling in MIN6 beta-cells by increasing nuclear beta-catenin and c-myc, a cWnt target gene. Rspo1 also induced insulin mRNA expression in MIN6 cells. Analysis of MIN6 and mouse beta-cell proliferation by [(3)H]thymidine and BrdU incorporation, respectively, revealed that Rspo1 stimulated cell growth. Incubation of MIN6 and mouse beta-cells with cytokines (IL1beta/TNFalpha/interferon-gamma) significantly increased cellular apoptosis; this increase was abolished by pretreatment with Rspo1. Rspo1 also stimulated insulin secretion in a glucose-independent fashion. We further demonstrated that the glucagon-like peptide-1 receptor agonist, exendin4 (EX4), stimulated Rspo1 mRNA transcript levels in MIN6 cells in a glucose-, time-, dose-, and PI3-kinase-dependent fashion. This effect was not limited to this beta-cell line, as similar time-dependent increases in Rspo1 were also observed in the betaTC beta-cell line and mouse islets in response to EX4 treatment. Together, these studies demonstrate that Rspo1 is a novel beta-cell growth factor and insulin secretagogue that is regulated by EX4. These findings suggest that Rspo1 and the cWnt signaling pathway may serve as a novel target to enhance beta-cell growth and function in patients with type 2 diabetes.
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Affiliation(s)
| | | | | | - Patricia L. Brubaker
- From the Departments of Physiology and
- Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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